This is an emulation of a Roman Abacus which probably never existed.
It is based on a Roman variant of the Salamis Tablet,
and is designed to match my Roman Calculator.
When the widget is started, it displays an abacus.
Click on the background to place a pebble on the abacus.
Click on a pebble to remove it from the abacus.
The number represented by the pebbles is displayed in both Roman and decimal notation.
Enter a Roman number (in compact format) into the upper field, then press RETURN.
The decimal equivalent is displayed and corresponding pebbles are placed on the abacus.
Enter a non-negative (decimal) number into the lower field, then press RETURN.
The Roman equivalent is displayed and corresponding pebbles are placed on the abacus.
The widget accepts non-negative javascript numbers.
If the alt-key is down when the RETURN key is pressed, the number is added to the number in the display and corresponding pebbles are placed on the abacus.
If the shift-key is down when the RETURN key is pressed, the number is subtracted from
the number in the display and corresponding pebbles are placed on the abacus.
The shift-key takes priority if the alt-key and shift-key are both down.
There are on-screen shift and alt keys primarily for use on tablet computers that do not have these keys available. They act as locking keys.
This is used to move the pebbles to the edges of the abacus, so that additional pebbles can be placed near to the centre line.
The display can be returned to a normal state by pressing RETURN in either the Roman or the decimal entry field. This generally reduces the number of pebbles and also moves the pebbles back to the centre line.
Roman numerals are M, D, C, L, X, V, I, S, ●, £, $, ℈ and ».
Fractions: » 1/1728 siliqua enter as " ℈ 1/288 scripulum enter as € $ 1/144 dimidia sextula £ 1/24 semuncia ● 1/12 uncia enter as u or U ●● 1/6 sextans ●●● 1/4 quadrans ●●●● 1/3 triens ●●●●● 5/12 quincunx S 1/2 semis S● 7/12 septunx S●● 2/3 bes S●●● 3/4 dodrans S●●●● 5/6 dextans S●●●●● 11/12 deinx Numerals: I 1 V 5 X 10 L 50 C 100 D 500 M 1000 (V) 5000 see note below ... (M) 1000000 ((V)) 5000000 ... ((M)) 1000000000
The notation used here for numbers of 5000 and above is not standard.
Parentheses () are used to indicate 1000 times the value of the number they enclose.
So 5000 is denoted by (V), 5000000 by ((V)) and so on.
10^9 is denoted by ((M)), not by (((I))).
The abacus displays Roman numbers of magnitude up to four billion ( < 4e9 ).
Roman numbers less than 1/3456 = 0.0002893519 (other than zero) cannot be displayed.
Roman numbers (other than zero) are rounded up by 1/3456.
Ancient Computers, Part I - Rediscovery, Edition 2 by Stephen Kent Stephenson, ISBN 9781490964379.
The Roman Abacus Web Widget is Copyright © 2020 Harry Whitfield (G6AUC).
This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version.
This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
You should have received a copy of the GNU General Public License along with this program; if not, write to the Free Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA